Help me design a 80dB opamp with 10uF capacitance load

[krishmaniac]

Re: A OPAMP design

where can i get that texas manual?? any link

 

[sergeyr77]

Re: A OPAMP design

With such a big Cload you can use 2 stage amplifier without compensation

 

[nxing]

A OPAMP design

Without specify which technology you will use, it's kind of hard to suggest the topology.

 

[hareesh]

A OPAMP design

ya folded casoce may work for the specification

 

[montage3000]

A OPAMP design

put the main pole at the output

 

[beckchm]

Re: A OPAMP design

using self-compensation

 

[laglead]

Re: A OPAMP design

Anyway you need a strong output buffer stage to reduce your output resisitance a lot.
I think you may need 3 stages: one input stage, one amplification stage and one output buffer stage.

 

[beckchm]

Re: A OPAMP design

you can use some other configuration

 

[ebalboni]

Re: A OPAMP design

The classic solution is to put a resistor in series with your load capacitor. Then at high frequencies the opamp load looks like a resistor. For example iof you place a 1kohm in series with your 10uf load the result at high frequencies will look like you are driving a 1kohm load. Of course it will take time to charge up the output.

 

[nickoo]

A OPAMP design

Class AB+Floaded-casecode is ok
It can push-pull high couple cap in audio application

 

[adwxl]

A OPAMP design

folded cascode opamp can solve this problem.

 

[pixel]

Re: A OPAMP design

Have you tried symetrical amplifier with OTA output?

 

[MLR67]

A OPAMP design

As Montage3000 told you : "put your main pole at the output "
it means the most suitable amplifier for your requierement (as I saw actually) is a OTA.

 

[wued]

Re: A OPAMP design

what is the app.

 

[lete]

A OPAMP design

I think folded cascode is very difficult to control Rout. We can use normal two-stage with high W/L in differential pair and choose suitable bias current.

 

[Analogworld]

Re: A OPAMP design

Folded cascode with gain boost auxiliary will be good enough for these specs.

 

[tuza2000]

A OPAMP design

gain boost+fold cascode
regards

 

[wangyuxin]

Re: A OPAMP design

so large load,it a hard job

 

[iocx]

A OPAMP design

Two-stage opamp is not suitable for this application.
Folded cascode OTA or with gain boost is your better choice.